Creating custom components with QT and use them into iOS and Android apps

I'm new in this forum and I would ask some questions about QT and custom components.

Right now I'm evaluating QT in order to share custom components among different platforms (iOS and Android right now). My goal is to create a component taht can be injected within each native apps I have (written in Java or Swift / Javascript). Here with the term component I mean an element that can be a non-UI one or a UI one (where the UI can be styled differently in iOS and Android in their native-look and feeling).

In addition, I would also like to know how many standard components QT provides and what is the chance to create a custom component based on the standard ones.